1. Field of the Invention
The present invention relates to a composite type recording apparatus including a recording medium and a non-volatile storage medium and adapted to write and read data according to a common file system and also to a data writing method and a data writing program for writing data to such a composite type recording apparatus.
2. Description of the Related Art
Hard disc drives (to be referred to as HDDs hereinafter) have been and are being used as external storages of personal computers (PCs). As the recording density of HDDs is improved, they are made to have a larger capacity. Large capacity HDDs are finding and expected to find applications in consumer level AV appliances such as AV home servers and electronic appliances mounted in cars.
In the current trend of downsizing the discs of HDDs, HDDs dimensionally in the order of 1.8 inches and 1 inch are expected to find applications in the field of mobile appliances such as digital still cameras (DSCs) and portable music players.
On the other hand, non-volatile semiconductor memories such as flash memories provide advantages including a low power consumption rate, a quick start feature and a high impact-resistance and large capacity non-volatile semiconductor memories with a memory capacity exceeding 1 GB have been developed. They are finding a variety of applications for their advantages.
Meanwhile, small storages to be used in mobile appliances particularly have to be available at low cost and show a high capacity, a low power consumption rate and a high responsiveness.
However, several seconds are necessary for HDDs after starting power supply to them until they get into an activated condition where they can record and reproduce data. On the other hand, non-volatile semiconductor memories are advantageous in terms of quick responsiveness of being able to be brought into an activated condition instantaneously. In short, a non-volatile semiconductor memory can record and reproduce data the instance when power is supplied to it.
If, on the other hand, an HDD is constantly held in an idling condition (a standby state for recording/reproduction), electric power is wasted to a significant extent to degrade the power consumption efficiency of mobile appliances whose power capacity is limited. Additionally, the HDD is accompanied by a disadvantage that the data transfer rate falls due to the use of an alternate process when a defective sector appears somewhere on the memory tracks.
Thus, development of hybrid storages of HDDs and non-volatile semiconductor memories that can offset the drawbacks of HDDs by means of the advantages of non-volatile semiconductor memories is expected. The inventors of the present invention have proposed a variety of arrangements for managing such hybrid storages by means of a single file system so as to fully exploit the potentials of such storages (see, inter alia, Patent Documents 1 through 4: Jpn. Pat. Appln. Laid-Open Publication Nos. 2003-123379, 2003-125358, 2002-150699 and 2000-324435).
For example, the system data necessary for accessing the software and the data to be used for controlling the HDD controller of an HDD has been stored in a predetermined region of the HDD and it is not possible to read out the system data until the HDD is activated. In other words, if power is supplied to an appliance where an HDD is mounted, it is not possible to use the appliance for some time after the start of power supply until the system data are read out from the HDD. In view of this problem, the above cited Patent Document 1 describes a technique for storing system data in a non-volatile semiconductor memory so as to make it possible to use the system data immediately after the start of power supply to the appliance.
As pointed out above, it takes several seconds for an HDD until it can record and reproduce data after the start of power supply and hence it is not possible for the HDD to record and reproduce data until it becomes active. In view of this problem, the above cited Patent Document 2 describes a technique of writing the data to be written in an HDD in a non-volatile semiconductor memory for a predetermined time period from the head thereof and subsequently, when the HDD is activated, writing the rest in the HDD in a data recording operation, while firstly reading the data written in the non-volatile semiconductor memory and subsequently, when the HDD is activated, reading the rest from the HDD in a data reproducing operation. With the arrangement of the Patent Document 2, it is possible to record and reproduce data immediately after the start of power supply to the appliance.
The above-cited Patent Document 3 describes a technique of preventing degradation of data transfer rate by utilizing a non-volatile semiconductor memory as spare region for a defective sector.
When an HDD is mounted in a video camera, there arises a risk of abruptly blocking the power supply when the video camera is dropped or otherwise subjected to impact while shooting an image. Then, it is no longer possible to reproduce the recorded data if a file system is not registered. To prevent such a situation from taking place, it is necessary to periodically update the file system in a predetermined region of the HDD but the operation of updating the file system remarkably reduces the data recording rate of the video camera. The Patent Document 4 describes a technique of protecting data without degrading the data transfer rate by assigning a region for updating the file system in the non-volatile semiconductor memory also mounted in the video camera.
In this way, it is possible to form a low cost and high performance storage by combining a small capacity non-volatile semiconductor memory and a large capacity HDD, utilizing the non-volatile semiconductor memory only as a data region to be used in a transitional condition and the HDD as a data region to be used in a steady state.